This invention relates to a surgical suture needle called "taper point-type."
A surgical suture needle of the taper point type, as disclosed in Japanese Laid-Open (Kokai) Patent application No. 309338/88, includes a proximal end portion defining a gut-mounting portion having a hole to which a gut is to be attached, an intermediate portion defining a main body portion having a generally uniform cross-sectional area throughout an entire length thereof, and a distal end portion defining a tapered portion whose cross-sectional area decreases progressively toward a pointed distal end of the suture needle. The tapered portion has no cutting edge.
The suture needle of the taper point type is caused to pierce the tissue, forcibly opening the tissue without cutting the tissue. A hole formed in the tissue as a result of the piercing of the suture needle therethrough is contracted or reduced in diameter after the passage of the suture needle therethrough, and a gut following the suture needle is brought into intimate contact with the inner periphery of this hole. Therefore, the suture needle of this type is used mainly for suturing the blood vessel.
In conventional suture needles of the taper point type, the tapered portion is short, and its length is about 2 to 7 times greater than the diameter of the main body portion. There are two reasons for this which are mentioned in the following.
Firstly, when the tapered portion is to be formed by grinding, the amount of grinding is intended to be reduced so as to shorten the time required for the grinding, thereby lowering the manufacturing cost.
Secondly, the resistance of the suture needle to the piercing through the blood vessel of the living body greatly depends on the degree of sharpness of the pointed end of the suture needle, and hardly depends on the amount (hereinafter referred to as "cross-sectional area increase rate") of increase of the cross-sectional area of the tapered portion per unit length from the pointed end toward the main body portion. Therefore, even if the tapered portion is made short, the piercing properties of the suture needle are not adversely affected. More specifically, the piercing resistance which the suture needle receives from the blood vessel of the living body is at the maximum level when piercing the skin of the blood vessel. This is due to the fact that the skin of the blood vessel has a greater rupture strength than the other parts of the blood vessel, and also due to the fact that the blood vessel of the living body has elasticity. The resistance of the suture needle to the piercing through the skin of the blood vessel greatly depends on the degree of sharpness of the point end of the suture needle. Once the suture needle pierces the skin of the blood vessel, the piercing resistance is abruptly reduced regardless of the value of the cross-sectional area increase rate of the tapered portion.
However, the above conventional suture needle of the taper point type has an inferior ability to pierce an artificial blood vessel which has been developed recently. This artificial blood vessel is formed by applying a special stretching process to polytetrafluoroethylene (PTFE), and is of an open-cell porous construction, and has the average pore size of about 30 micron meters, that is, has a fibril length of about 30 micron meters. It has been confirmed that such an artificial blood vessel has an excellent compatibility with the living body, and can withstand the blood pressure for a long period of time.